Twins, their age matched siblings and parents are studied to obtain an accurate estimate of facial, dental,and somatic growth, including their interralationships, with reference to growth rates and patterns, physique, nutrition, physiologic and chronologic age scales. A total a 531 twin pairs have collaborated in this study of whom 385 were like sexed and 148 of unlike sex. However, 93 pairs withdrew from the study after their first examination, leaving a total sample of 438 of which presently 292 pairs are active. The contribution of genetic and environmental influences to individual differences in growth rate, size and form at different periods of development will be determined together with an assessment of the short-term predictability of facial growth.